display 和 position的用法：
学习一点儿css，应该系统地看一遍的，否则，用到的时候就比较浪费时间了；
曾经总在div的布局上花费时间，今天才发现是因为display属性没有看明白。h1，p，div等元素默认是display:block的，所以，两个div 挨着就总换行； span，a等元素默认display:inline 的，所以，两个span挨着就不会自动换行； 现在，了解了 display属性后，就可以方便地控制他们是否换行了。
通过：
<style> div {display:inline}<style> 就可以让div也不换行了
通过：
<style> span{display:block}<style> 也可以让span换行了
参考资料：
http://www.w3schools.com/css/css_display_visibility.asp
http://www.w3schools.com/css/css_positioning.asp
http://www.w3schools.com/css/css_float.asp
http://www.zhangxinxu.com/wordpress/?p=1565
IN http://www.w3schools.com/css/css_align.asp
Crossbrowser Compatibility Issues
When aligning elements like this, it is always a good idea to predefine margin and padding for the <body> element. This is to avoid visual differences in different browsers.
There is a problem with IE8 and earlier, when using the position property. If a container element (in our case <div>) has a specified width, and the !DOCTYPE declaration is missing, IE8 and earlier versions will add a 17px margin on the right side. This seems to be space reserved for a scrollbar. Always set the !DOCTYPE declaration when using the position property: